WO2020137355A1 - Solid electrolyte material and battery using same - Google Patents

Abstract

Provided is a solid electrolyte material having a high lithium ion conductivity. This solid electrolyte material has a crystal structure including a skeleton structure and an ion-conducting species. The skeleton structure contains a one-dimensional chain that is formed of multiple polyhedra that share vertices and are linearly connected. Each of the multiple polyhedra contains at least one type of cation and one type of anion.

Description

Solid electrolyte material and battery using the same

The present disclosure relates to a solid electrolyte material and a battery using the solid electrolyte material.

Patent Document 1 discloses an all-solid-state battery using a sulfide solid electrolyte. Patent Document 2 discloses an all-solid-state battery using a halide solid electrolyte containing indium.

Japanese Patent Laid-Open No. 2011-129313 JP, 2006-244734, A Y. Li, C. Wang, H. Xie, J. Cheng and J. B. Goodknow, Electrochem. Commun. , 2011, 13, 1289-1292. H. Chen, L. L. Wong and S. Adams, Acta Crystallogr. , Sect. B: Struct. Sci. , Cryst. Eng. Mater. , 2019, 75, 18-33.

An object of the present disclosure is to provide a solid electrolyte material having high lithium ion conductivity.

The solid electrolyte material of the present disclosure has a crystal structure including a skeleton structure and an ion-conducting species, and the skeleton structure includes a one-dimensional chain in which a plurality of polyhedra are linearly connected with a vertex in common. The plurality of polyhedra include at least one cation and at least one anion.

The present disclosure provides a solid electrolyte material having high ionic conductivity.

FIG. 1 shows a cross-sectional view of a battery 1000 according to the second embodiment. FIG. 2 shows a schematic diagram of a pressure molding die 300 used for evaluating the ionic conductivity of a solid electrolyte material. FIG. 3 shows a crystal structure of a solid electrolyte material having a composition represented by LiNbOCl ₄ . FIG. 4 shows a structure of the crystal structure in FIG. 3 viewed from the a-axis direction. FIG. 5 shows the result of Rietveld analysis performed on the solid electrolyte material of Example 1 using the crystal structure shown in FIG. FIG. 6 shows a crystal structure of the solid electrolyte material according to Comparative Example 2.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

(First embodiment)
The solid electrolyte material according to the first embodiment has a crystal structure including a skeleton structure and an ion conductive species. The skeletal structure includes a one-dimensional chain in which a plurality of polyhedrons share a vertex and are linearly connected. Each plurality of polyhedra comprises at least one cation and at least one anion.

The solid electrolyte material according to the first embodiment has high ionic conductivity. Therefore, the solid electrolyte material according to the first embodiment can be used to obtain a battery having excellent charge/discharge characteristics. An example of the battery is an all solid state secondary battery.

One polyhedron is formed from one cation and all anions bound to the cation. The cations are located inside the polyhedron and the anions are located at the vertices of the polyhedron. If the distance between the cation and the anion is less than 1.2 times the sum of the atomic radii of the cation and the anion, the cation can be considered to be bound to the anion.

The one-dimensional chain in the present disclosure refers to a structure in which a plurality of polyhedra share a vertex with each other and are linearly connected. Hereinafter, the anion arranged at the apex is also called a shared anion.

Since the skeletal structure of the solid electrolyte material is composed of one-dimensional chains, the packing rate of the crystal structure (that is, the volume ratio of the constituent elements to the entire crystal structure) becomes low. This is because in a skeletal structure consisting of one-dimensional chains, the distance between the atoms that form one polyhedron and the atoms that form another polyhedron is larger than in a skeletal structure that consists of two-dimensional chains or three-dimensional chains. Is. In a crystal structure having a low packing factor, there are few atoms that hinder the ionic conduction of the ionic conducting species. That is, the ionic conduction path of the ionic conduction species is large. Furthermore, since the distance between the ion-conducting species and the anions constituting the skeleton structure is large, electrostatic interaction between the ion-conducting species and the anions is small. As a result, the ionic conductivity of the solid electrolyte material is increased.

When multiple polyhedra share a vertex, the gap between the polyhedra becomes larger than when they share faces or edges. That is, the filling rate of the crystal structure becomes low. This widens the conduction path of the ion conductive species, and further increases the ionic conductivity of the solid electrolyte material.

The shared anion may be one kind or two or more kinds. If the number of shared anions is one, the bond distance between the cation and each shared anion will be similar. As a result, distortion of the polyhedron is reduced, and the polyhedron has a shape close to a regular polyhedron. This allows the polyhedron to exist more stably.

It is desirable that the solid electrolyte material according to the first embodiment does not contain sulfur. The solid electrolyte material containing no sulfur is excellent in safety because it does not generate hydrogen sulfide even when exposed to the atmosphere. It should be noted that the sulfide solid electrolyte disclosed in Patent Document 1 may generate hydrogen sulfide when exposed to the atmosphere.

The polyhedron may be a tetrahedron or an octahedron. Such polyhedra tend to form one-dimensional chains.

The polyhedra may be octahedra to form one-dimensional chains with less distortion.

The anion forming the polyhedron may be one kind or two or more kinds. When the polyhedron contains two or more kinds of anions, the polyhedron can realize various shapes. As a result, the stability and ionic conductivity of the solid electrolyte material can be improved. When the number of shared anions is one and the anions other than the shared anions are different from the shared anions, the polyhedron has a shape close to a regular polyhedron, and the stability of the solid electrolyte material is improved. When the number of shared anions is 2 or more, the polyhedron has a distorted shape of a regular polyhedron. As a result, the stability of the solid electrolyte material may be reduced, but the strain may reduce the filling rate of the crystal structure. Due to these, the solid electrolyte material has high ionic conductivity.

The polyhedron comprises at least one cation selected from the group consisting of Nb, Ta, and P and at least one anion selected from the group consisting of O, F, Cl, Br, and I. Good. The solid electrolyte material composed of such a polyhedron has high ionic conductivity.

The ion conductive species may be lithium ion. Since lithium ions have a small ionic radius, they are easily conducted in the crystal.

The shape of the solid electrolyte material according to the first embodiment is not limited. Examples of the shape are acicular, spherical, or elliptical spherical. The solid electrolyte material according to the first embodiment may be particles. The solid electrolyte material according to the first embodiment may be formed to have a pellet or plate shape.

For example, when the shape of the solid electrolyte material according to the first embodiment is particulate (for example, spherical), the solid electrolyte material may have a median diameter of 0.1 μm or more and 100 μm or less, and preferably, It may have a median diameter of 0.5 μm or more and 10 μm or less. As a result, the solid electrolyte material according to the first embodiment has higher ionic conductivity. Furthermore, the solid electrolyte material according to the first embodiment and other materials can be well dispersed.

In order to favorably disperse the solid electrolyte material and the active material according to the first embodiment, the solid electrolyte material according to the first embodiment may have a median diameter smaller than that of the active material.

The solid electrolyte material according to the first embodiment may further contain different crystal phases.

The crystal structure of the solid electrolyte material is evaluated by Rietveld analysis. The Rietveld analysis is a method that mainly determines the crystal structure of the target sample based on the diffraction peak angle and the intensity of the X-ray diffraction pattern obtained by the X-ray diffraction method. The Rietveld method uses, for example, the methods described in Chapters 7, 8 and 9 of "Actual powder X-ray analysis, second edition (edited by Asakura Shoten, Izumi Nakai, Fujio Izumi)". Specifically, the X-ray diffraction pattern of the solid electrolyte material to be analyzed is measured by the θ-2θ method in the range where the diffraction angle 2θ is 10° or more and 80° or less. The RIETAN-2000 program is used for the obtained X-ray diffraction pattern, and Rietveld analysis is performed. The reliability of the analysis result is evaluated based on, for example, the R _wp value.

<Method for producing solid electrolyte material>
The solid electrolyte material according to the first embodiment is manufactured, for example, by the following method.

Raw powders are mixed so as to have a desired composition. Examples of raw material powders are halides, oxides, hydroxides, or acid halides. The raw powders may be mixed in pre-adjusted molar ratios to offset the compositional changes that may occur during the synthesis process.

Raw materials are reacted with each other mechanochemically (that is, using the method of mechanochemical milling) in a mixing device such as a planetary ball mill to obtain a reaction product.

In this way, the solid electrolyte material according to the first embodiment is obtained.

(Second embodiment)
The second embodiment will be described below. The matters described in the first embodiment are omitted as appropriate.

The battery according to the second embodiment includes a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is arranged between the positive electrode and the negative electrode.

At least one selected from the group consisting of a positive electrode, an electrolyte layer, and a negative electrode contains the solid electrolyte material according to the first embodiment. The battery according to the second embodiment contains the solid electrolyte material according to the first embodiment, and thus has high charge/discharge characteristics.

A specific example of the battery according to the second embodiment will be described below.

FIG. 1 shows a sectional view of a battery 1000 according to the second embodiment.

The battery 1000 includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is arranged between the positive electrode 201 and the negative electrode 203.

The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100.

The electrolyte layer 202 contains an electrolyte material (for example, a solid electrolyte material).

The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100.

The solid electrolyte particles 100 are particles made of the solid electrolyte material according to the first embodiment or particles containing the solid electrolyte material according to the first embodiment as a main component. The particle containing the solid electrolyte material according to the first embodiment as a main component means a particle in which the most contained component is the solid electrolyte material according to the first embodiment.

The positive electrode 201 contains a material capable of inserting and extracting metal ions (for example, lithium ions). The material is, for example, a positive electrode active material (for example, positive electrode active material particles 204).

Examples of positive electrode active materials are lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanion materials, transition metal sulfides, transition metal oxyfluorides, transition metal oxysulfides, or transition metal oxynitrides. .. Examples of lithium-containing transition metal oxides are Li(NiCoAl)O ₂ , LiCoO ₂ , or Li(NiCoMn)O ₂ .

The positive electrode active material particles 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles 204 have a median diameter of 0.1 μm or more, the positive electrode active material particles 204 and the solid electrolyte particles 100 can be favorably dispersed in the positive electrode. This improves the charge/discharge characteristics of the battery. When the positive electrode active material particles 204 have a median diameter of 100 μm or less, the diffusion rate of lithium in the positive electrode active material particles 204 is improved. This allows the battery to operate at high power.

The positive electrode active material particles 204 may have a median diameter larger than that of the solid electrolyte particles 100. Thereby, the positive electrode active material particles 204 and the solid electrolyte particles 100 can be favorably dispersed.

From the viewpoint of the energy density and output of the battery, in the positive electrode 201, the ratio of the volume of the positive electrode active material particles 204 to the total volume of the positive electrode active material particles 204 and the solid electrolyte particles 100 is 0.30 or more and 0.95 or less. May be

From the viewpoint of the energy density and output of the battery, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. The electrolyte layer 202 may be a solid electrolyte layer.

The electrolyte layer 202 may be composed only of the solid electrolyte material according to the first embodiment.

It may be composed only of a solid electrolyte material different from the solid electrolyte material according to the first embodiment. Examples of the solid electrolyte material different from the solid electrolyte material according to the first embodiment are Li ₂ MgX′ ₄ , Li ₂ FeX′ ₄ , Li(Al,Ga,In)X′ ₄ , and Li ₃ (Al,Ga,In). ) X′ ₆ or LiI. Here, X′ is at least one element selected from the group consisting of F, Cl, Br, and I.

Hereinafter, the solid electrolyte material according to the first embodiment is referred to as a first solid electrolyte material. The solid electrolyte material different from the solid electrolyte material according to the first embodiment is called the second solid electrolyte material.

The electrolyte layer 202 may contain not only the first solid electrolyte material but also the second solid electrolyte material. In the electrolyte layer 202, the first solid electrolyte material and the second solid electrolyte material may be dispersed uniformly.

The layer made of the first solid electrolyte material and the layer made of the second solid electrolyte material may be stacked along the stacking direction of the battery 1000.

The electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less. When the electrolyte layer 202 has a thickness of 1 μm or more, the positive electrode 201 and the negative electrode 203 are less likely to be short-circuited. If the electrolyte layer 202 has a thickness of 1000 μm or less, the battery can operate at high power.

The negative electrode 203 contains a material capable of inserting and extracting metal ions (for example, lithium ions). The material is, for example, a negative electrode active material (for example, negative electrode active material particles 205).

Examples of the negative electrode active material are metallic materials, carbon materials, oxides, nitrides, tin compounds, or silicon compounds. The metal material may be a simple metal or an alloy. Examples of metallic materials are lithium metal or lithium alloys. Examples of carbon materials are natural graphite, coke, graphitizing carbon, carbon fibers, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, a preferable example of the negative electrode active material is silicon (that is, Si), tin (that is, Sn), a silicon compound, or a tin compound.

The negative electrode active material particles 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material particles 205 have a median diameter of 0.1 μm or more, the negative electrode active material particles 205 and the solid electrolyte particles 100 can be favorably dispersed in the negative electrode 203. This improves the charge/discharge characteristics of the battery. When the negative electrode active material particles 205 have a median diameter of 100 μm or less, the diffusion rate of lithium in the negative electrode active material particles 205 is improved. This allows the battery to operate at high power.

The negative electrode active material particles 205 may have a median diameter larger than that of the solid electrolyte particles 100. Thereby, the negative electrode active material particles 205 and the solid electrolyte particles 100 can be favorably dispersed.

From the viewpoint of the energy density and output of the battery, in the negative electrode 203, the ratio of the volume of the negative electrode active material particles 205 to the total volume of the negative electrode active material particles 205 and the solid electrolyte particles 100 is 0.30 or more and 0.95 or less. May be

From the viewpoint of the energy density and output of the battery, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 contains a second solid electrolyte material for the purpose of enhancing ionic conductivity, chemical stability, and electrochemical stability. May be

The second solid electrolyte material may be a sulfide solid electrolyte.

Examples of sulfide solid electrolytes are Li ₂ S—P ₂ S ₅ , Li ₂ S—SiS ₂ , Li ₂ S—B ₂ S ₃ , Li ₂ S—GeS ₂ , Li _3.25 Ge _0.25 P _{0. 0.75} S ₄ or Li ₁₀ GeP ₂ S ₁₂ .

The second solid electrolyte material may be an oxide solid electrolyte.

Examples of oxide solid electrolytes are:
(I) a NASICON-type solid electrolyte such as LiTi ₂ (PO ₄ ) ₃ or its element substitution body,
(Ii) (LaLi) perovskite solid electrolyte such as TiO _{3,
(Iii) Li 14 ZnGe 4 O} 16, Li 4 SiO 4, LiGeO 4 or LISICON solid electrolyte such as its elemental substituents,
(Iv) a garnet-type solid electrolyte such as Li ₇ La ₃ Zr ₂ O ₁₂ or an element-substituted product thereof, or (v) Li ₃ PO ₄ or an N-substituted product thereof.

The second solid electrolyte material may be an organic polymer solid electrolyte.

Examples of organic polymer solid electrolytes are polymer compounds and lithium salt compounds. The polymer compound may have an ethylene oxide structure. Since the polymer compound having an ethylene oxide structure can contain a large amount of lithium salt, the ionic conductivity can be further increased.

Examples of the lithium _{salt, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiSO 3 CF 3, LiN (SO 2 CF 3) 2, LiN (SO 2 C 2 F 5) 2, LiN (SO 2 CF 3) (SO ₂ C ₄ F ₉ ) or LiC(SO ₂ CF ₃ ) ₃ . One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used.

At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 is a non-aqueous electrolyte solution, a gel electrolyte, or an ion for the purpose of facilitating the transfer of lithium ions and improving the output characteristics of the battery. It may contain a liquid.

The non-aqueous electrolyte solution contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents are cyclic carbonate solvents, chain carbonate solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, or fluorine solvents. Examples of cyclic carbonic acid ester solvents are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of chain ester carbonate solvents are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of chain ether solvents are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a chain ester solvent is methyl acetate. Examples of fluorine solvents are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethylmethyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone. Alternatively, a mixture of two or more non-aqueous solvents selected from these may be used.

Examples of the lithium _{salt, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiSO 3 CF 3, LiN (SO 2 CF 3) 2, LiN (SO 2 C 2 F 5) 2, LiN (SO 2 CF 3) (SO ₂ C ₄ F ₉ ) or LiC(SO ₂ CF ₃ ) ₃ . One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, 0.5 mol/liter or more and 2 mol/liter or less.

A polymer material impregnated with a non-aqueous electrolyte may be used as the gel electrolyte. Examples of polymeric materials are polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethylmethacrylate, or polymers with ethylene oxide linkages.

Examples of cations contained in ionic liquids are:
(I) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium,
(Ii) Pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, or aliphatic cyclic ammoniums such as piperidiniums, or (iii) pyridiniums or nitrous-containing heteroatoms such as imidazoliums It is a ring aromatic cation.

Examples of anion contained in the ionic _{^{liquid, PF 6 -, BF 4 -}} , SbF 6- -, AsF 6 -, SO 3 CF 3 -, N (SO 2 CF 3) 2 -, N (SO 2 C 2 F _{^{5) 2 -, N (SO}} 2 CF 3) (SO 2 C 4 F 9) -, or _{C (SO 2 CF 3) 3} - a.

The ionic liquid may contain a lithium salt.

At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder for the purpose of improving the adhesion between particles.

Examples of the binder are polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, Polyacrylic acid hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid hexyl ester, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyether sulfone, hexafluoropolypropylene, styrene butadiene rubber , Or carboxymethyl cellulose. Copolymers can also be used as binders. Examples of such binders are tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid. , And a copolymer of two or more materials selected from hexadiene. A mixture of two or more materials selected from these may be used as the binder.

At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive for the purpose of enhancing electron conductivity.

Examples of conductive aids are
(I) graphites such as natural graphite or artificial graphite,
(Ii) carbon blacks such as acetylene black or Ketjen black,
(Iii) conductive fibers such as carbon fibers or metal fibers,
(Iv) carbon fluoride,
(V) Metal powders such as aluminum,
(Vi) conductive whiskers such as zinc oxide or potassium titanate,
(Vii) a conductive metal oxide such as titanium oxide, or (viii) a conductive polymer compound such as polyaniline, polypyrrole, or polythiophene. The conductive aid of the above (i) or (ii) may be used for cost reduction.

Note that examples of the shape of the battery according to the second embodiment are coin type, cylindrical type, square type, sheet type, button type, flat type, or laminated type.

(Example)
Hereinafter, the present disclosure will be described in more detail with reference to examples.

(Example 1)
[Preparation of solid electrolyte material]
LiCl and NbOCl ₃ were prepared as raw material powders in a dry atmosphere having a dew point of −30° C. or lower so that the molar ratio of LiCl:NbOCl ₃ was 1:1. These materials were crushed and mixed in a mortar to obtain a mixed powder. The obtained mixed powder was milled at 600 rpm for 24 hours using a planetary ball mill. Thus, the powder of the solid electrolyte material according to Example 1 was obtained. The solid electrolyte material according to Example 1 had a composition represented by LiNbOCl ₄ .

[Evaluation of ionic conductivity]
FIG. 2 shows a schematic diagram of the pressure molding die 300 used for evaluating the ionic conductivity of the solid electrolyte material.

The pressure molding die 300 had an upper punch portion 301, a frame die 302, and a lower punch portion 303. The frame mold 302 was made of insulating polycarbonate. The punch upper part 301 and the punch lower part 303 were formed of electronically conductive stainless steel.

Using the pressure molding die 300 shown in FIG. 2, the ionic conductivity of the solid electrolyte material was measured by the following method.

The powder of the solid electrolyte material according to Example 1 (that is, the powder 101 of the solid electrolyte material in FIG. 2) was filled in the pressure molding die 300 in a dry atmosphere having a dew point of −30° C. or lower. A pressure of 400 MPa was applied to the solid electrolyte material according to Example 1 by using the punch upper part 301 and the punch lower part 303.

The upper punch 301 and the lower punch 303 were connected to a potentiostat (Princeton Applied Research, VersaSTAT 4) equipped with a frequency response analyzer while pressure was applied. The punch upper part 301 was connected to a working electrode and a potential measuring terminal. The punch lower part 303 was connected to the counter electrode and the working electrode. The ionic conductivity of the solid electrolyte material according to Example 1 was measured by an electrochemical impedance measuring method.

As a result, the ionic conductivity measured at 25°C was 5.7 mS/cm.

[X-ray diffraction]
X-ray diffraction measurement was performed on the solid electrolyte material according to Example 1. An X-ray diffractometer (RIGAKU, MiniFlex 600) was used for the measurement. The X-ray diffraction pattern of the solid electrolyte material according to Example 1 was measured in a dry atmosphere having a dew point of −45° C. or lower. Cu-Kα rays were used as the X-ray source. That is, an X-ray diffraction pattern was measured by the θ-2θ method using Cu-Kα rays (wavelengths 1.5405Å and 1.5444Å) as X-rays. The measurement result is shown in FIG. 5 as a “measurement pattern”.

[Riet belt analysis]
Rietveld analysis was performed on the solid electrolyte material according to Example 1 using the crystal structures shown in FIGS. 3 and 4. The analysis result is shown in FIG. 5 by a solid line as a “simulation pattern”. The peak position calculated from the crystal structure of FIG. 3 and the X-ray diffraction pattern of the solid electrolyte material according to Example 1 were substantially the same. The R _wp value was 4.76. This can be said to be a sufficiently low value with reference to Non-Patent Document 1, for example. Therefore, the solid electrolyte material according to Example 1 has the crystal structure shown in FIGS. 3 and 4. That is, the solid electrolyte material according to Example 1 had a skeleton structure and ion-conducting species, and the skeleton structure was composed of a one-dimensional chain in which a plurality of polyhedra were connected linearly with their vertices in common. The bottom line in FIG. 5 represents the difference in the diffraction intensity between the measured value and the calculated value. The small difference in the diffraction intensity proves that the analysis result is highly reliable.

(Comparative Example 1)
The solid electrolyte material according to Example 1 was heat-treated at 300° C. for 3 hours in an argon atmosphere having a dew point of −60° C. or lower. Thus, the powder of the solid electrolyte material according to Comparative Example 1 was obtained.

The ionic conductivity of the solid electrolyte material according to Comparative Example 1 was measured in the same manner as in Example 1. As a result, the ionic conductivity was 1.6×10 ⁻⁴ mS/cm.

Rietveld analysis was performed on the solid electrolyte material according to Comparative Example 1 by using the crystal structure of the solid electrolyte material according to Example 1. As a result, the R _wp value was 28.4. Since the R _wp value is large, it cannot be regarded as a similar crystal structure. That is, it is considered that the solid electrolyte material according to Comparative Example 1 does not have the one-dimensional chain structure shown in FIGS. 3 and 4.

[Evaluation of activation energy]
Using the method described in Non-Patent Document 2, the activation energy of the solid electrolyte material according to Example 1 was calculated. The calculated values are shown in Table 1.

The crystal structures of the solid electrolyte materials of Examples 2 to 6 were obtained as follows.

(Example 2)
In the crystal structure of the solid electrolyte material according to Example 1, Cl was replaced with F as an element. The crystal structure was then optimized by first-principles calculations. The first-principles calculation was performed by the PAW (Projector Augmented Wave) method based on the density functional theory. In optimizing the crystal structure, GGA-PBE was used to describe the electron density that expresses the exchange correlation term, which is the interaction between electrons. GGA stands for Generalized Gradient Application. PBE stands for Perdew-Burke-Ernzerhof.

(Example 3)
In the crystal structure of the solid electrolyte material according to Example 1, Cl was elementally replaced by Br. The crystal structure was then optimized by first-principles calculations. The first-principles calculation was performed under the same conditions as in Example 2.

(Example 4)
In the crystal structure of the solid electrolyte material according to Example 1, Cl was replaced by I. The crystal structure was then optimized by first-principles calculations. The first-principles calculation was performed under the same conditions as in Example 2.

(Example 5)
In the crystal structure of the solid electrolyte material of Example 1, Nb was replaced with Ta. The crystal structure was then optimized by first-principles calculations. The first-principles calculation was performed under the same conditions as in Example 2.

(Example 6)
In the crystal structure of the solid electrolyte material according to Example 1, Nb was replaced with P. The crystal structure was then optimized by first-principles calculations. The first-principles calculation was performed under the same conditions as in Example 2.

The activation energies of the solid electrolyte materials according to Examples 2 to 6 were calculated in the same manner as in Example 1. The calculated values are shown in Table 1.

(Comparative example 2)
A crystal structure (mp-755505) of Li ₂ NbOF ₅ was obtained from the first principles calculation database Materials Project. In the crystal structure, the crystal structure was optimized by first-principles calculation after F was replaced by Cl. The first-principles calculation was performed under the same conditions as in Example 2. The activation energy was calculated for the optimized crystal structure in the same manner as in Example 1. The optimized crystal structure is shown in FIG. As is clear from FIG. 6, the polyhedra did not share vertices. Moreover, the polyhedra did not form one-dimensional chains. The activation energy values of the solid electrolyte material according to Comparative Example 2 are shown in Table 1.

In Table 1, “one-dimensional activation energy” means “one-dimensional conduction path activation energy”. The same applies to “two-dimensional” or “three-dimensional”.

(Discussion)
As is clear from Table 1, the solid electrolyte materials according to Examples 1 to 6 having a skeleton structure composed of one-dimensional chains have particularly low one-dimensional activation energy. Therefore, the solid electrolyte materials according to Examples 1 to 6 have high ionic conductivity.

As is clear from the comparison of Example 1 with Comparative Example 2, even if they have the same constituent elements but do not have one-dimensional chains, the activation energy becomes high.

In the two-dimensional conduction path and the three-dimensional conduction path of the solid electrolyte materials according to Examples 1 to 6, the ionic conduction species need to pass through the one-dimensional chains, so that the activation energy of the two-dimensional and three-dimensional is one-dimensional. It will be higher than the activation energy. However, it has lower two-dimensional and three-dimensional activation energies than the solid electrolyte material according to Comparative Example 2 having no one-dimensional chain. It is considered that this is because in the solid electrolyte materials according to Examples 1 to 6, the polyhedrons are linearly connected with the vertices shared, so that the packing rate of the crystal structure is low and the ionic conduction path is wide. To be

The solid electrolyte material of the present disclosure is used, for example, in an all solid lithium ion secondary battery.

100 Solid Electrolyte Particles 101 Solid Electrolyte Material Powder 201 Positive Electrode 202 Electrolyte Layer 203 Negative Electrode 204 Positive Electrode Active Material Particles 205 Negative Electrode Active Material Particles 300 Pressure Molding Dies 301 Punch Upper 302 Frame Mold 303 Punch Lower 1000 Battery

Claims (7)

Has a crystal structure including a skeletal structure and an ionic conducting species,
The skeletal structure includes a one-dimensional chain in which a plurality of polyhedra are linearly connected with each other by sharing a vertex,
Each said plurality of polyhedra comprises at least one cation and at least one anion,
Solid electrolyte material. The polyhedron is an octahedron,
The solid electrolyte material according to claim 1. The element arranged at the apex is one kind of anion,
The solid electrolyte material according to claim 1. The polyhedron contains two or more anions,
The solid electrolyte material according to any one of claims 1 to 3. The polyhedron comprises at least one cation selected from the group consisting of Nb, Ta, and P, and at least one anion selected from the group consisting of O, F, Cl, Br, and I.
The solid electrolyte material according to any one of claims 1 to 4. The ion conductive species is lithium ion,
The solid electrolyte material according to any one of claims 1 to 5. Positive electrode,
A negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode,
At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material according to any one of claims 1 to 6,
battery.

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